These special clothes, tattoos and other accessories are largely user-driven, as in, Red Light Center doesn’t directly help or support with them. However, there is a large bank of textures available in the Forums, under the ‘Textures: Clothing, Tattoos, etc’ thread on the main page and in the catalog here.

Also, if you see someone in world with a tattoo or a piece of clothing you would like, feel free to ask them to give you the file so you can add it onto your character as well.